Phosphorous (P) is an essential dietary nutrient for growth. It was found in the conventional animal feed such as grain, oilseed meal, by-product from seed that a large quantities of phosphorous is in presence of phosphate covalently bonded in phytic acid molecule. However, non-ruminant animals such as fowls and pigs lack digestive enzymes for separating inorganic phosphorus from the phytic acid molecule, so that a coefficient of utilization of phosphorus is very low.
Incapability of utilizing the phytic acid for the non-ruminant animal results in extra cost incurred from the addition of inorganic phosphorus such as calcium dihydrogen phosphate and defluorinated phosphate, or animal products such as meat, bone meal, and fish meal. In addition, the phytic acid combines with several essential minerals, such as calcium, zinc, iron, magnesium and copper, preventing or inhibiting the absorption of the minerals in the digestive tract. Therefore, a large amount of undigested phytate phosphorous in animal feeds was excreted, increasing the ecological phosphorus burden to the environment.
Addition of microbial phytases as feed additive improved the bioavailability of phytic acid in the non-ruminant animal's feed, so as to decrease the addition of inorganic phosphorus, and reduce the amount of phosphorus excreted in poultry manner. Also, the phytase may be applied to produce the feed ingredient with the lower continent of Calcium-magnesium phytate.
In spite of the well-known benefits of use of phytase including addition to animals feed and human's food, it was surprising that a little phytase was widely accepted and applied to feed, and starch liquefaction and alcohol fermentation industry, due to the phytase's properties being incapable of meeting the requirement of the application environment. It was the most important properties including high specific activity, low optimal pH, High resistance to pepsin and trypsin, and thermostability for the phytase being applied to starch liquefaction as feed enzyme, since the phytase would be exposed to the increasing temperature, such as 70 to 95° C. during feed pelleting technologies, and 75 to 120° C. during starch liquefaction technology.
The gene sequence of the phytase appA from Escherichia coli was provided by Dassa et al. in 1990 (J. Bact. P5497-5500, 1990). The phytase appA has the improved specific activity which 30-40 times larger than that of Aspergillus niger phytase, but was limited in its wide application to feed and starch liquefaction due to its thermostability. Many mutations to E. coli phytase had been started in the different commercial order, based on its inherent characteristics. The order of the present invention is to provide a phytase with the modified and improved temperature characteristic, not limited to the thermostability and the optimal temperature in the embodiment.